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The two primary hazards associated with flammable and combustible liquids are explosion and fire.

Safe handling and storage of flammable liquids requires the use of approved equipment and practices per OSHA standards.

The determining factor in whether a liquid is flammable or combustible is its flashpoint. Flashpoint:  The minimum temperature at which a liquid gives off enough vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid. Remember, it is the vapors, not the liquid, that Burns! A chemical’s flashpoint is listed on the MSDS under the Fire and Explosion section.

Flash point means the minimum temperature at which a liquid gives off enough vapor to form an ignitable mixture. In general, the lower the flash point, the greater the hazard. Flammable liquids have flash points below 100 deg. F, and are more dangerous than combustible liquids, since they may be ignited at room temperature. NFPA Classes IA, IB, & IC Combustible liquids have flash points at or above 100 deg. F. NFPA Classes II & IIIA & B Although combustible liquids have higher flash points than flammable liquids, they can pose serious fire and/or explosion hazards when heated.

Flammable Liquid Classifications Any liquid having a flashpoint below 100 deg. F (37.8 deg. C) or higher, the total of which make up 99 percent or more of the total volume of the mixture.  Flammable liquids shall be known as Class I liquids.  Class I liquids are divided into three classes as follows: Class IA - shall include liquids having flashpoints below 73 F (22.8 C) and having a boiling point below 100 F (37.8 C). Class IB - shall include liquids having flashpoints below 73 F (22.8 C) and having a boiling point at or above 100 F (37.8 C). Class IC - shall include liquids having flashpoints at or above 73 F (22.8 C) and below 100 F (37.8 C).

Combustible Liquid Classifications Any liquid having a flashpoint at or above 100 deg. F (37.8 deg. C).  Combustible liquids shall be divided into two classes as follows: Class II - shall include those with flashpoints at or above 100 F (37.8 C) and below 140 F (60 C), except any mixture having components with flashpoints of 200 F (93.3 C) or higher, the volume of which makes up 99 percent or more of the total volume of the mixture. Class III - shall include those with flashpoints at or above 140 F (60 C). Class III liquids are subdivided into two subclasses: Class IIIA - shall include those with flashpoints at or above 140 F (60 C) and below 200 F (93.3 C), except any mixture having components with flashpoints of 200 F (93.3 C), or higher, the total volume of which makes up 99 percent or more of the total volume of the mixture. Class IIIB - shall include those with flashpoints at or above 200 F (93.3 C).

Some Flammable Liquids in the Plant: Triethalemine 17 deg. F Barsol A-2316 54 deg. F Acetone Solvent 0 deg. F Barsol A-2343 56 deg. F Barsol A-3447 0 deg. F N-Butanol 36 deg. F Sec. Butanol 72 deg. F Glycol Ether 94 deg. F      Enamel Reducer 20 deg. F Isopropyl Alcohol 45 deg. F Methanol 45 deg. F MEK 23 deg. F Xylene 79 deg. F Toluene 45 deg. F Gasoline -50 deg. F 142 Solvent 66/3 610 F

Explosive limits involve the concentration level of the given chemical in the air. In popular jargon, a vapor/air mixture below the flammable limit is too lean to burn or explode.  A mixture above the upper flammable limits is too rich to burn. Most flammable liquids are volatile, meaning they evaporate quickly, and can reach a concentration in the air that could lead to an explosion.

Lower and Upper Explosive Levels (LEL/UEL)

A good plan for safe use of flammable and combustible liquids contains at least these components: Control of the ignition sources. Practice safe handling, storage, fire control and ventilation. Identify sources of ignition. Always use bonding and grounding when transferring flammable liquids into/from containers. Always provide adequate ventilation to reduce the potential for ignition. Proper storage Ensure flammables and combustibles are properly stored. Identify compatible chemicals. Isolate and separate incompatible materials. Ensure storage doesn’t limit safe egress. Store in proper area, cabinet, or container. Label storage areas/cabinets. Store waste and residue in covered containers and dispose of daily. Fire control Ensure proper hoses, fire extinguishers or other fire control devices are available where flammable or combustible liquids are stored. Do not permit flames or smoking in areas where flammable or combustible liquids are stored. Store materials that react with water in a room separate from flammable and combustible liquids. Safe handling Transfer by means of a safety pump. Transfer by gravity through an approved self-closing safety faucet. Transfer through a closed piping system. Transfer from safety cans.

Some sources of ignition for flammable and combustible liquids: open flames smoking cutting and welding hot surfaces electrical and mechanical sparks static electricity lightning

Static Electricty         Static Electricty is generated when a fluid flows through a pipe or from an opening into a tank. The main hazards are fire and explosion from sparks containing enough energy to ignite the flammable vapors. Bonding or grounding of the flammable liquid containers is necessary to prevent static electricity from causing a spark.

Bonding         Physically connect two conductive objects together with a bond wire to eliminate a difference in static charge potential between them. You must provide a bond wire between containers during flammable liquid filling operations, unless a metallic path between them is otherwise present

Grounding         Eliminates a difference in static charge potential between conductive objects and the ground. Although bonding will eliminate a difference in potential between objects, it will not eliminate a difference in potential between these objects and earth unless one of the objects is connected to the earth with a ground wire.

Ventilation Always provide adequate ventilation to reduce the potential for ignition of flammable vapors.

Storage of Flammable and Combustible Liquids Identify incompatible chemicals – check the Material Safety Data Sheet Isolate and separate incompatible materials Isolate by storing in another area or room. The degree of isolation depends on the quantities, chemical properties and packaging. Separate by storing in the same area or room, but apart from each other. Storage must not limit the use of exits, stairways, or areas normally used for the safe egress of people. In office occupancies: Storage is prohibited except that which is required for maintenance and operation of the equipment. Storage must be in: Closed metal containers inside a storage cabinet. Safety cans. Inside a storage room.

Safety Cans for Storage and Transfer         Approved container of not more than 5 gallons capacity. Spring-closing lid and spout cover Safely relieves internal pressure when exposed to fire

Flame Arrester Screen         Prevents fire flashback into the can contents. Double wire-mesh construction. Large surface area provides rapid dissipation of heat from fire so that vapor temperature inside the can remains below ignition point.

Storage Cabinets                  Not more than 60 gallons of Class I and/or Class II liquids, or not more than 120 gallons of Class III liquids are permitted in a cabinet. The cabinet must be conspicuously labeled, “Flammable - Keep Fire Away”. The doors on the metal cabinets must have a three-point lock (top, side, and bottom), and the door sill must be raised at least 2 inches above the bottom of the cabinet.

Fire Control         Suitable fire control devices, such as a small hose or portable fire extinguishers must be available where flammable or combustible liquids are stored. Open flames and smoking must not be permitted in these storage areas. Materials which react with water must not be stored in the same room with flammable or combustible liquids

Transferring Flammable Liquids Since there is a sizeable risk whenever flammable liquids are handled, OSHA allows only four methods for transferring these materials: Through a closed piping system From safety cans By gravity through an approved self-closing safety faucet By means of a safety pump

Self-Closing Safety Faucet         Bonding wire between drum and container. Grounding wire between drum and ground. Safety vent in drum.

Safety Pump         Faster and safer than using a faucet. Spills less likely. No separate safety vents in the drum are required Installed directly in drum bung opening Some pump hoses have integral bonding wires

Waste and Residue Combustible waste and residue must be kept to a minimum, stored in covered metal receptacles and disposed of daily. Waste drum with disposal funnel Safety disposal can Oily-waste can (self-closing lid)

Safe Handling Fundamentals Carefully read the manufacturer’s label on the flammable liquid container before storing or using it. Practice good housekeeping in flammable liquid storage areas. Clean up spills immediately, then place the cleanup rags in a covered metal container. Only use approved metal safety containers or an original manufacturer’s container to store flammable liquids. Keep the containers closed when not in use and store away from exits or passageways. Use flammable liquids only where there is plenty of ventilation. Keep flammable liquids away from ignition sources such as open flames, sparks, smoking, cutting, welding, etc.

Remember: The two primary hazards associated with flammable and combustible liquids are explosion and fire.

Return to the FPT 102 - Fire Prevention and Inspection Course Flammable and Combustible liquids slide.